It's still four years to go until the next US presidential election, but already the Republicans are having cold sweats over the prospect of facing Hillary Clinton at the ballot box, judging by the comments of Newt Gingrich.

The one-time challenger for the party's 2012 White House nod expressed the thought that many of his GOP colleagues must be harbouring, but are too timid to mention: If Clinton decides to stand in 2016, they are toast.

"If the competitor in 16 is going to be Hillary Clinton, supported by Bill Clinton and presumably a still relatively popular President Barack Obama, trying to win that will be truly the Super Bowl," Gingrich told Meet the Press on NBC. "And the Republican party is incapable of competing at that level."

It has become the parlour game of the moment to wonder whether Clinton will run for the White House in 2016 once she stands down as secretary of state, which the New York Times says will be soon after the inauguration of Obama's second term next month. Should she decide to make a bid, her current popularity levels, at 61%, would make her a shoo-in for the Democratic nomination.

Gingrich's frank words are revealing because they show how fearsome the Democratic trinity of the two Clintons and Obama appears to the Republicans. "She is married to the most popular Democrat in the country. They both think it would be good for her to be president. That makes it virtually impossible to stop her for the nomination, I think," he said

Gingrich, who knows all about the terrifying powers of the Clintons having been Republican House speaker during the Bill Clinton administration, went further, saying that the Republican party in its current guise would be ill-equipped to take them on.

"We didn't blow it because of Mitt Romney," he told NBC. "We blew it because of a party which has refused to engage the reality of American life and refused to think through what the average American needs for a better future."

Still, Gingrich's penetrating soul-searching about the competence of the GOP to take back the White House appears not to extend to his own political suitability for the highest office. Asked whether he would put himself forward in 2016 he said: "I doubt it," but then added: "One never knows."